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Energy 101: Geothermal Heat Pumps

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An energy-efficient heating and cooling alternative, the geothermal heat pump system moves heat from the ground to a building (or from a building to the ground) through a series of flexible pipe "loops" containing water. This edition of Energy 101 explores the benefits Geothermal and the science behind how it all comes together.

MR. : We all want to save money heating or cooling our house or office, right? The answer may be under your feet, literally. Much of the heating and cooling can come from the ground, below the surface, with something called a geothermal heat pump. You see, below the frost line about 10 feet down, the Earth maintains a nearly constant temperature of 54 degrees. We can tap into this energy to provide heating in the winter and cooling in the summer.

OK, now, here’s how it works. Bury a loop of pipes called a heat exchanger just below the surface, and fill them with water or a water and antifreeze solution. During the winter months, the air is usually cooler than the temperature below ground. The solution circulates in a loop underground and absorbs the Earth’s heat. This heat is brought to the surface and transferred to a heat pump. The heat pump warms the air, and then your regular heating system warms the air some more to a comfortable temperature. Finally, ducts circulate the air to the various rooms.

Now, a huge benefit is that the geothermal system doesn’t have to work as hard to make people inside comfortably warm, and you save lots of money on your heating bill. In the summertime, the system works in reverse. When it’s hot outside the temperature below the surface is cooler than the summer heat. So the fluid in the loop absorbs heat in the building and sends it underground. The ground’s lower temperature cools it, and it’s circulated again and again. Now you’re saving money on air conditioning.

Now, this church uses a large geothermal heat pump to heat and cool the building. It has a very big parking lot, which lets it spread out is loop horizontally. But if you don’t have all that space, you can go straight down and use a vertical loop system instead.

Geothermal heat pumps can be used just about anywhere in the U.S. because all areas have nearly constant shallow-ground temperatures, although systems in different locations will have varying degrees of efficiency and cost savings.

The constant temperature of the Earth just below our feet is a sustainable resource literally in our own backyard. It’s a clean energy source ready for us to use to heat and cool our homes and buildings while lowering our utility bills.